The aim of the proposed research is to investigate the roles of granulosa cell estradiol (E) and progesterone (P) in the regulation of mammalian oocyte maturation. The following hypotheses will be tested: A relatively high ratio of E:P in the cumulus/membrana granulosa cell syncitium results in heterologous transfer of E into the oocyte; this transfer serves to maintain the concentration of E within the oocyte above a threshold level required for synergism between E and cyclic adenosine monophosphate (cAMP) to maintain meiotic arrest; the luteinizing hormone (LH)-induced increase in synthesis by the granulosa cells of P relative to E, results in decreased transfer of E and in a subsequent reduction in the concentration of E within the oocyte below the threshold level required to prevent reinitiation of meiosis. In vivo studies with cycling and gonadotropin-primed hamsters will be employed for this research in which meiotic status will be determined after interference with: (1) pre-ovulatory E using non-steroidal E-antagonists and E-specific antiserum; and (2) the LH-induced increase in P, using P-specific antiserum and an anti-P monoclonal antibody. The E-antagonists will be administered peripherally; the antisera and monoclonal antibody will be pressure-injected locally into the follicle in anesthetized animals. Meiotic status will be scored cytogenetically after preparation of chromatin spreads. The concentrations of E and P in both serum and follicular fluid, and that of cAMP in the oocyte and cumulus cell compartments, will be determined by RIA. Heterologous metabolic coupling will be measured using an assay system with radiolabeled uridine. Transfer of E into the oocyte will be investigated using radiolabeled uptake studies and column and high-pressure liquid chromatographic analyses. Cellular integrity and viability will be assessed by electron microscopy. It is anticipated that this research will define the relationships which exist between E and P in the regulation of maturation. The long-term objective is to elucidate the physiological mechanisms that regulate oocyte maturation. This process is fundamental to successful fertilization and consequent propagation of a species. Determination of these regulatory mechanisms is, therefore, essential if highly specific means of contraception are to be directed at the level of the oocyte, and if problems of human infertility related to oocyte development are to be clinically treated.